Gas case-hardening furnace



Patented Mar. l, 1938 UNITED STAT'ES PATENT oFFc;

2,o9,7`- GAS CASE-HARDENING'FURNACE Leon Saives, Billancou't,-Francej'assignor to Louis Renault, Blllancourt, France ApplicationSeptember 9, 1936, Serial No. 100954 France July 16', 1036 V 1Claim.(crees-is 7 W The present invention relates to improvements in gascase-hardening i'urnaces.

An object of the invention resides in the provislon of means forensuring rapid diflusion of the freshgases entering the furnace by'whirling the gases into the muflle chamber of 'the i'urnace. Anotherobject of the invention is to provide means onthe outside of the iurnacewhich will force fresh gases into the mufile, chamber in such 10 amanner that the added gases are more thdroughly mixed with the gasesalready i the furnace to thus obtain substantially the same temperatureand* chemical composition throughout the iurnace,

In order to `allow of ready comprehension of the invention, it will be-more particularly described with reference to the attached drawin inwhich:

The single figure is a transverse section of 'a muflle furnace furnishedwith a device for the diffusion of fresh gas.

The improvement relates to the gas inlets and has for eiect therendering certain of :the diflusion of the fresh gas by energeticstirring inside the furnace.

This device assures uniform distribution of the chemical composition andof the temperature.

The characteristic of this device resides in the fact that no stirringfan is introduced into the 3 iurnace because the oonstruction ot suchfans iscomplicated and the working detective; especially at hightemperatures when case-hardening with ca rbon.

The drawing shows one example of construction. e

The cementing gas arrives at l into the chamber 2 which provides ahousing for a centrifugal 'ran 3. The fan has a radial projectingaction' but there is no r'dial o'utlet in the chanber 2 40 and the gascan escape only by way of an axial cone 4 terminated by a connectingpiece 4 opening at a suitable place into the cementing mume 5. The gasby action of the fan receives a gyratory movement but the speed ofmotion in the direction of the axis ofthe fan.'is not substantiallyincreased. The shaft 6 ot the fan' which leaves the chamber 2 through astumng box 'l is guided in bearings 8 and 9 and driven by amotor -Il bymeans of a flexible coupling lfl. The

-5o cementing muille i is housed inthe inside' of a iurnace representedby its refractory iining fl! and insulating lining ll. The mume restson` roller-s ll allowing its !ree expanson; The ob- ;leci-.s to becase-hardened IS are put on tables I! which 'are pushed end to end intothe mume i.

' *the connecting piece 4 i I Upon entering the muflle 5,-the gas givesrise 1.',

`3 which is outside o! theurnace and remains The method of 'working isas followsz in the first place theflow ot cementing gas in 1 is adjustedto suit requirements. By reason of the rotation of the tan 3 the gas'isanimatedby'an intense gyratorymovement; By 'application of the theoremof kinetic moment, and 'since thegyrat- .ing gas is confined in the cone4, the moment oi the quantity of movement is constant, and the speed ofrotation of a molecule of gas is inversely proportional to its distancefrom the axis of the cone.

As, the gasdescends in the cone 4 its speed 'of rotation increasesandbecomes very' great in to a vortex with vertical axis which fillsthe. whole section of the, mome. `Moreover, in the axis of this cyclonethere is produced a vacuum which sucks up the gas from below to abovealong the axis while the gas whirls in descending near the walls ofthemuflle. v

This *energetic stirring assured the ho'nogeneity of distribution of thetemperature 'and of the chemical composition; even in the vicinity 'oithe gas inlet connectiom There is thus avoided the dissociation orenergetic cracking to which the new cementing ga's would give rise ifitwere not first diluted in' a great mass oi' gas already in equilibriumwith the temperature. e

It thus results that the cmenting is much' V more constant and. moreregular.

Owing to the arrangement oi' the stirring Ian cool, 'its construction iseasy and its working cer- 35 tain. The therm'al eflliency 'is excellent.

Finally, the cementing is very regular andretains all its eflicacy inthe concave parts and bores of the objects treated.` I

^ I claim:

In a gas case-hardening furnace a muille chamber, means for introducingcementing gas into the' muflle chamber comprisinga centrifugal fanhaving a, gas supply communicating therej 45 with, means for' rotatingthe Ian, a housing'forthe fan having a downwardly extending conei shapedportion with the apex thereof communicating with said muille chamber,whereby'the gas is moved into the chanber by whirling the molecules ofthe same in the cone-shaped housingand ison serves;

